1. Field of the Invention
The present invention relates to wastewater treatment plants and, more particularly, to a wastewater treatment plant for residential usage that is compact, can be easily handled as a single unit, and does not require excavations of varying depths.
2. Description of the Prior Art
Typical wastewater treatment plants of the type under consideration comprise a pretreatment tank or vessel, commonly referred to as a trash tank, an aerobic treatment vessel, generally comprised of an aerobic treatment chamber and a clarifier chamber, and a holding vessel, commonly referred to as a pump tank. As is well known to those skilled in the art, the wastewater flows into the trash tank, where solids settle. A liquid effluent from the trash tank flows into the aerobic treatment vessel and, more specifically, the aerobic treatment chamber where it is aerated, the aerated liquid being discharged from the clarification chamber into the holding or pump tank from whence it can be discharged for irrigation purposes at appropriate times, generally at night. Flow between the three vessels or tank is accomplished by gravity. Accordingly, either the vessels or tanks must be at successively lower levels or the plumbing connections between the various tanks set at proper elevations to ensure gravity flow.
While there are prior art single structure design systems that obviate the necessity for excavations at various levels to accommodate the three vessels, such systems are quite bulky, require a large excavation, and are difficult to handle. There are also one-piece systems formed of three separate compartments, each of the compartments having a riser or hatch that protrudes above ground. There are still other one-piece systems that are subject to uneven loading in the event the volume in the pump tank drops to a low level. Such uneven loading can result in flotation shifting in areas with a high water table and in certain cases can place excessive stresses on the system. Lastly, there are three vessel systems in which separate vessels are banded together with steel bands in an attempt to form a unitary system.
There still remains a need for a single unit system that can be easily transported, handled, and installed, requires only one excavation at one elevation, minimizes the number of risers protruding above ground, and distributes the loading on the system, substantially preventing any tendency of the unit to float or undergo bending stresses in areas having a high water table and when the volume of the pump tank or chamber is at a low level.
It is therefore an object of the present invention to provide a wastewater treatment plant that is compact.
Another object of the present invention is to provide a unitary wastewater treatment plant that is easy to handle and requires only a single excavation at one elevation for installation.
Yet a further object of the present invention is to provide a wastewater treatment plant that minimizes the number of above-ground risers.
Still a further object of the present invention is to provide a unitary wastewater treatment plant that remains weight-balanced despite the level of water in the holding or pump chamber.
The above and other objects of the present invention will become apparent from the drawings, the description given herein, and the appended claims.
The wastewater treatment plant of the present invention comprises a first containment vessel and a second containment vessel, the second containment vessel forming an aerobic treatment chamber, the second containment vessel having an inlet and an outlet. A compartment is formed in the first containment vessel, the compartment and the first containment vessel cooperating to form a pretreatment chamber inside the compartment and a holding chamber formed by the compartment and the first containment vessel. Both the pretreatment chamber and the holding chamber have an inlet and an outlet, the outlet from the pretreatment chamber being in open communication with the inlet to the second containment vessel, the outlet from the aerobic treatment chamber being in open communication with the inlet to the holding chamber.